1. Field of the Invention
This invention relates to a process for the production of water-soluble cationic polymers. More particularly the invention relates to a process for producing water-soluble, substantially solid, cationic polymers by irradiating a high concentration aqueous solution of a monomer or monomers selected from the group consisting of tertiary and quaternary salts of aminoalkyl acrylate and aminoalkyl methacrylate, said monomer solution optionally containing acrylamide, with ionizing radiation in the presence of a specifically selected alcohol.
2. Description of Prior Art
Cationic polymers of the tertiary or quaternary salts of aminoalkyl acrylate or methacrylate having the generic formula: ##STR3## wherein, R.sub.1 represents a hydrogen atom or a methyl group; R.sub.2 represents a hydrogen atom or an alkyl group having 1-4 carbon atoms; R.sub.3 and R.sub.4 each represents an alkyl group having 1-4 carbon atoms; Y represents an alkylene group having 1-4 carbon atoms and X.sup.(-) represents an anion; or cationic copolymers of said tertiary or quaternary salts with acrylamide, are known. Such cationic polymers have a variety of uses as a high polymeric flocculant material to be used in industrial water, in service water or in sewage, or in the field of mining, public works and the like for the purposes of promoting settling out or floating upwards of fine particles suspended in each liquid, or they can also be used as a dewatering aid for sludge from waste water purification process.
These cationic polymers or copolymers have hitherto been prepared by solution-polymerization in water under irradiation or in the presence of an initiator of polymerization such as a peroxide or a redox catalyst. These methods of polymerization, however, have defects in that since the polymerization is carried out in the solution of relatively low monomer concentration, the polymer is obtained as a mass in the state of a gel accompanied by a large amount of water, and accordingly the molecular weight thereof decreases as time elapses and in addition, since the mass is in the state of a gel, it is expensive to transport it.
For these reasons, it has been proposed and tried to separate solid polymer from the mass in the state of a gel containing water by means of, for example, the precipitation of the solid polymer in an organic solvent such as methanol and acetone, or alternatively by drying the gelatinous mass in hot air to remove water therefrom. In any of these methods, complicated additional steps are generally required to follow the step of the aqueous solution polymerization and improvement of these points has been desired.
As a result of thorough investigation with respect to the production of cationic polymers by irradiation, we have found that it is possible to obtain a substantially solid polymer in yield of 100% by irradiating a highly concentrated aqueous solution of at least one member selected from the group consisting of tertiary and quaternary salts of aminoalkyl acrylate and methacrylate, or a mixture of said member and acrylamide. However, the polymer thus obtained is water-insoluble and therefore its use is limited to only a few industrial applications.
Hereupon, we have further studied to find a method of preventing the product polymer from becoming water-insoluble and have finally found that it is possible to obtain a water-soluble polymer if we carry out the polymerization by irradiating an aqueous high concentration solution of a monomer or monomers with ionizing radiation in the presence of a specific alcohol under specific conditions. Based on this discovery, the present invention has been accomplished.